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OCR A2 CHEMISTRY F324 and F325- 14th and 22nd June 2016- OFFICIAL THREAD watch

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    (Original post by Matteus3)
    Same, even if it's wrong you only lose like 1 mark though, so glad Chem is over😃
    Now it's time for bio tomorrow and C4 Friday then freeddoooomm 😭🙌🏾
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    (Original post by getoverhere)
    what was the balanced equation for the redox reaction of iodine in alkaline?
    3i2 + 6oh- --> io3- + 3h2o + 5i-
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    (Original post by d14m)
    X=4 anyone?


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    Almost everyone :P
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    (Original post by Vannzzoo)
    I got X as 4 not really sure tho, overall it was alright
    Didn't finish. Got Mr as something like 225 which would have led me to an x of 4.

    I suspect i got around 85
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    What did everyone get for the buffer? My pH was 3 point something but I think it's wrong


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    (Original post by Kvothe the arcane)
    Didn't finish. Got Mr as something like 225 which would have led me to an x of 3.

    I suspect i got around 85
    Well done
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    (Original post by oliversquares201)
    What numbers did people get for the maths based questions?
    I remember getting 2.3 and 2.82 somewhere and 10 point something
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    (Original post by adetutu)
    3i2 + 6oh- --> io3- + 3h2o + 5i-
    That was the only question I left blank. I kept coming back to it but just wasn't getting it. *shrug* It was only 1 mark
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    Did anyone get 3.93 as the buffer and around 10.67/76 (cant remeber exactly) for ph of NaOH
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    (Original post by medic1010101)
    What did everyone get for the buffer? My pH was 3 point something but I think it's wrong


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    I got around that too, I thought it was wrong too but I worked it out again and got the same answer?

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    (Original post by Kvothe the arcane)
    Didn't finish. Got Mr as something like 225 which would have led me to an x of 4.

    I suspect i got around 85
    Aah damn, you were seconds from finishing haha! Well done though, I expect you'd only have gained a mark or two from having the time to finish that.
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    (Original post by medic1010101)
    What did everyone get for the buffer? My pH was 3 point something but I think it's wrong

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    I think go got 10 point something not sure tho
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    Answer dump:
    Q3: -1099 DHhyd
    -43.05
    Q4 104 Kc dm3mol-1
    Q5 ph 2.12
    3.43 ph buffer
    13.03
    ph naoh dilute 10.76

    x=4
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    (Original post by Vannzzoo)
    I remember getting 2.3 and 2.82 somewhere and 10 point something
    10.46 for the pH of the base?😁

    What did people put for whether a pH of 7 was neutral, alkaline or acidic at 60'C?
    I wasn't sure what calculation to do
    I worked out [H+] for a pH of 7 using the kW from 60 degrees. Then I used 1 as my moles of OH- and put that 7 is alkaline at 60 degrees because my answer for [H+] was less? I'm sure I'm not right. I had to take a guess

    I must have missed a stoichiometry adjustment somewhere because I got 881kJmol-1 for the hydration of sulphate calculation
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    (Original post by RealistZ)
    Did anyone get 3.93 as the buffer and around 10.67/76 (cant remeber exactly) for ph of NaOH
    Yeah!!!!
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    (Original post by RealistZ)
    Did anyone get 3.93 as the buffer and around 10.67/76 (cant remeber exactly) for ph of NaOH
    I got something like this but cant remeber exactly.
    I struggled so badly on the Kw question 😭
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    What did you guys get for the enthalpy change question?
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    (Original post by KB_97)
    For the buffer solution question there was 0.05 moles of na(can't remember what it was) and 0.04 moles of the weak acid. Which means all the weak acid was used up. How can that be a buffer solution? I still used those number anyway to calculate a ph but I knew it was wrong. I just didn't know what else to do
    I think you were supposed to calculate the moles of the first solution, then use that to calculate the concentration of the 100cm solution,then use that for the buffer pH calculation, well that's what I did at least
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    (Original post by KB_97)
    For the buffer solution question there was 0.05 moles of na(can't remember what it was) and 0.04 moles of the weak acid. Which means all the weak acid was used up. How can that be a buffer solution? I still used those number anyway to calculate a ph but I knew it was wrong. I just didn't know what else to do
    I put the A- excess into a ka equation to try to find the H+ conc? I was clutching at straws though, only used it because we were told the ka or kpa? Probably wrong but that's whati tried to do.
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    (Original post by KB_97)
    For the buffer solution question there was 0.05 moles of na(can't remember what it was) and 0.04 moles of the weak acid. Which means all the weak acid was used up. How can that be a buffer solution? I still used those number anyway to calculate a ph but I knew it was wrong. I just didn't know what else to do
    Because it only dissociates as far as Ka
 
 
 
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